1. Field of the Invention
The present invention relates to an exposure apparatus that projects an original pattern onto a substrate via a projection optical system and a liquid, and exposes the substrate to light, and relates to a method of manufacturing a device using the apparatus.
2. Description of the Related Art
With advances in the miniaturization of semiconductor devices, exposure light sources used have shifted from high-pressure mercury lamps (for g and i lines) to KrF excimer lasers and ArF excimer lasers, that is, light sources that emit light having shorter wavelengths. In order to obtain higher resolutions, the NAs (Numerical Apertures) of projection optical systems need to be increased. This leads to the tendency toward smaller depths of focus. The relationship between them can be generally expressed by:(resolution)=k1(λ/NA)(depth of focus)=±k2(λ/NA2),where λ is the wavelength of the exposure light, NA is the numerical aperture of a projection lens, and k1 and k2 are coefficients dependent on processes.
As a technique for higher resolutions and larger depths of focus, a technique using a phase shift mask or modified illumination has been studied and put into practice. As another technique for higher resolutions and larger depths of focus, an immersion exposure technique is known. The immersion exposure technique is a technique of exposing a substrate to light via a liquid having a high refractive index between the final surface of a projection optical system and a substrate (image surface).
If the liquid supplied in the space between the final surface of the projection optical system and the image surface leaks, due to some reason, the leakage may affect electronic devices, mechanisms, and the like, in the exposure apparatus. The occurrence of leakage of the liquid requires a long period of maintenance time for restoration, resulting in a deterioration in productivity. In particular, if the power supplied to the exposure apparatus is shut off at the time of an emergency, even during the operation of the apparatus, the liquid remains on a substrate or the substrate stage, and may leak thereafter.
Japanese Patent Laid-Open No. 2005-079480 discloses a technique of tilting a substrate stage to make a liquid flow into a liquid recovery groove formed in advance in the stage at the time of power failure. Japanese Patent Laid-Open No. 2005-268742 discloses a technique of preventing adverse effects on other peripheral electronic devices, and the like, by stopping the supply of a liquid and specifying a leakage portion by using a leakage detection mechanism at the time of an emergency, for example, a power failure. Japanese Patent Laid-Open No. 2006-179761 discloses a technique using a plurality of power supply systems.
The techniques disclosed in each of Japanese Patent Laid-Open Nos. 2005-079480, 2005-268742, and 2006-179761 can be understood to be a technique of preventing the leakage of a liquid when the power supplied to an immersion exposure apparatus is shut off. The techniques disclosed in each of Japanese Patent Laid-Open Nos. 2005-079480, 2005-268742, and 2006-179761 do not propose any specific sequence by which the supply of power is shut off upon reception of a power-off request. Furthermore, the techniques disclosed in each of Japanese Patent Laid-Open Nos. 2005-079480, 2005-268742, and 2006-179761 do not propose to quickly recover the liquid on a substrate or the substrate stage when the supply of power is shut off. Moreover, the techniques disclosed in each of Japanese Patent Laid-Open Nos. 2005-079480, 2005-268742, and 2006-179761 do not propose to control recovery of the liquid by a method corresponding to trouble that has occurred in a power supply system.